The object of this project is to delineate the mechanism of mitogen stimulation of B and T lymphocytes by an analysis of the mitogen-membrane interactions and the mechanisms by which these interactions initiate or suppress cellular response. To this end we have isolated and identified the major cell surface acceptors for both mitogenic and non-mitogenic lectin on both T and B cells from mice. Further studies by blocking and/or capping those acceptors with antibodies, and by chemical modification of mitogens suggest that there is not a critical receptor, but that cell stimulation is triggered by a more general and complex set of interactions. These studies have been carried out with murine lymphocytes and now are being expanded to include human cells. Preliminary results indicate that human lymphocytes respond somewhat differently than their murine counterparts. The carbohydrate specificity of Pa-2, the major mitogen from pokeweed, has also been determined. In collaboration with other units of NIH, work is in progress in the chemical structure of secretory IgA, especially the binding of secretory component and on the structure and origin of amyloid proteins of unknown origin. Studies on the primary sequence of guinea pig B, S and Ia membrane glycoproteins have been initiated.